Process of metal coating or filling



Patented May 29, 1934 UNITED STATES PROCESS lVIETAL COATING PR FILLING Alvin P. Bixler, Duncannon, Pa., assignor to Advance Engineering Corporation, Duncannon, Pa., a corporation of Pennsylvama No Drawing. Application August 26, 1931, Serial No. 559,591

2 Claims. (Cl. Bl-70.1)

My invention relates to .improvements in the process of metal coating or filling and has to do,

. more particularly, with the process of applying heavy coatings or fillings on metal by means of 5 the metal spray.

The metal spray, or what is more generally termed the Schoop process, has been used, recently, for the purpose of filling dents, holes, and the like in metallic objects. In the use of this process for filling dents in the sheet metal panels of automobile bodies and similar objects, it has been found necessary, heretofore, either to roughen up the surface to be filled by means of a burring tool or sand blast, or to drive pins or the like into the object to provide a surface to which the sprayed filling or coating may anchor itself me chanically. In actual practice such roughening or pinning takes up the major portion of the time required for the repair or coating operation. Furthermore, it has been found that the filling or coating is imperfectly bonded to the surface thus prepared and in many instances the filling or heavy coating eventually becomes detached. Adhesive priming coats of such material as rubber cement have been used to cause sprayed coatings to adhere, but my experience has been that in the case where the metal coating is heavy, or in the nature of a filling, the adhesion provided by the rubber cement is wholly inadequate.

With the above methods and attendant problems in view, my invention has for its primary object the provision of a method of preparing a metallic surface for metal spraying which meth- 0d is rapid and results in a great saving in time over the roughening procedure now employed.

Another object of my invention is to provide a method of preparing a metallic surface for metal spraying which method results in a perfect bond of the sprayed metal to the surface of the coated or filled object.

Further objects and objects relating to details and economies of composition and use willdefinitely appear from the detailed description to follow.- In one instance I accomplish the objects of my invention by the means and procedure set forth in the following specification. My invention is clearly defined in the appended claims.

In general, my invention relates to spray coating with metal in a cool, more or less plastic state, and consists in the substitution, for the present procedure of roughening, pinning, or applying an adhesive coating upon the surface to be sprayed, of an operation with a novel composition which, without the application of high temperature, fluxes the cool but plastic sprayed metal particles into perfect union approaching a state of amalgamation with the surface metal of the object coated thereby.

More specifically my invention consists in removing whatever paint, dirt or grease is upon the surface of the object to be coated or filled, applying a small quantity of a special cold-tinning flux to the surface with a small swab of waste or excelsior, rubbing the flux into a complete coating and adherence with the entire surface to be sprayed, wiping off all but the tenacious film formed on the surface, and spraying the coating or filling metal directly upon the thus prepared surface. For preparing the surface of ferrous objects for spraying with lead-tin alloys, my preferred cold-tinning flux comprises, by weight:

In preparing the above composition, the mercuric chloride, copper sulphate, mercury and emery dust are mixed together with suificient water to form a pasty mass. To this pasty mass is added glycerine, which reduces the paste to a consistency most desirable for easy application. The active chemical agents are the mercuric chloride, copper sulphate and mercury, the emery dust serving as an abrading agent causing the active agents to come into perfect union with the ferrous surface of the object to be sprayed. The water and glycerine serve as the vehicle and thinning agent for the composition. While I have disclosed emery dust as a desirable abrading agent, I have found that ground glass is a suitable material for this purpose. Furthermore, ground glass is a splendid filler and maybe added in comparatively large quantities for the purpose of increasing the bulk of the composition without decreasing its efficiency. The cost of the composition is thereby materially decreased and economies are thus effected.

In cold tinning aluminium or aluminium containing alloys, the above composition is not generally satisfactory. However, I have found that by the admixture of a small quantity of silver nitrate to the above composition a very satisfactory cold-tin aluminium fiuxis provided. The following formula, however, represents the composition of what I have found to be a most satisfactory cold flux for aluminium:

To which is added ground glass as abrasive agent and bulk-increasing material to an amount short of interference with the efficiency of the chemical agents.

By way of explanation, I believe the action of my cold-tin fiux, rubbed into complete wetting contact with the metallic surface to be coated or filled, to be in the nature of an amalgamizing of the contained mercury with a superficial surface portion of the object. Lead-tin alloys such as common solder, when sprayed upon thus prepared metallic surfaces, have an adherence or bonding therewith far superior to the purely mechanical union provided by roughening the surface. As is well known, particles projected from the spray gun used in Schoop processing are not hot as in the case of soldering with torch or iron, but are in a cool, more or less plastic condition. Heat, therefore, constitutes no part of the fluxing operation embodying my invention. A flexible sheet of steel prepared and sprayed in accordance with my invention may be repeatedly folded or bent until torn, yet the sprayed coating will not separate along its surface of contact with the sheet. A perfect bond of sprayed metal to base metal is provided, which bond can not be accomplished by the now used roughening procedure of surface preparation.

I am aware that satisfactory cold-tin flux may be provided in accordance with my invention even though the relative quantities of the constituents be varied considerably. Other sulphates such as zinc sulphate for example may be used in place of copper sulphate. Further, in the case of other metal objects and other coating metals, simple or alloyed, addition agents may be found which improve the bond or reduce the cost of the flux composition disclosed as illustrative of my invention. For'example, I have found that by adding a small quantity of finely divided metal, such as fine particles of 60-4O solder, my fiux becomes much more efiective for use in preparing Bonderized metallic objects. I, therefore, claim my invention broadly as indicated by the appended-claims.

What I claim is:

l. The method of providing an intimately bonded coating or filling of metal upon an aluminous surface, which comprises cleaning said surface, applying thereto an aqueous mixture of mercuric chloride, copper sulphate and silver nitrate, rubbing said mixture into perfect wetting contact with said surface, wiping from said surface all but the thin tenacious film of mercury formed thereon, and spraying the coating or filling metal upon the thus prepared surface in the form of finely divided plastic particles.

2. The method of providing a lead or lead alloy coating or filling upon an aluminous surface, which comprises cleaning said surface, applying thereto an aqueous mixture of metallic-mercury, mercuric chloride, copper sulphate and silver nitrate, rubbing the mixture into perfect wetting contact with said surface, wiping from said surface all but the thin tenacious film of mercury formed thereon, and spraying the lead or lead alloy coating or filling upon the thus prepared surface in the form of finely divided particles.

ALVIN P. BIXLER. 

